Product Overview
The Allen-Bradley 1746-NO4I is a four-channel analog output module built for the SLC 500 platform. It produces a current output range of 0 to +20 mA, which makes it suitable for driving modulating instruments and devices. This module works with both fixed and modular SLC 500 hardware styles, giving engineers flexibility during system design and upgrades.
If you are maintaining an existing SLC 500 installation, this module often serves as a direct replacement for aging analog output cards. The 1746-NO4I uses a 16-bit two’s complement binary format and provides a converter resolution of 14 bits via the R-2R ladder conversion method.
Technical Specifications
| Specification | Value |
|---|---|
| Module Type | Analog Output Module |
| Outputs | Four (4) |
| Output Current Range | 0 to +20 mA |
| Full Scale Output | 21 mA |
| Resolution | 14 bits |
| Update Time | 512 microseconds |
| Step Response | 2.5 milliseconds |
| Backplane Current (5 VDC) | 55 milliamps |
| Backplane Current (24 VDC) | 195 milliamps |
| Load Range | 0 to 500 ohms |
| Operating Temperature | 0 to 60 degrees Celsius |
The 14-bit resolution gives you fine control over analog signals, which matters when your process demands precise valve positioning or accurate signal retransmission. The 512-microsecond update time keeps all four channels refreshed quickly in parallel, so your control loop stays responsive. With a load range of 0 to 500 ohms, the module handles a broad set of field devices without additional signal conditioning.
Why Engineers Choose This Module
When you are specifying an analog output card for a PID control loop, signal stability and update speed are critical. The 1746-NO4I addresses both. Its step response of 2.5 milliseconds at 95% means the output reaches its target value quickly, reducing lag in your control system. The overrange capability of 5% (0 to +21 mA minus 1 LSB) provides headroom for demanding applications.
This module also includes an embedded selector switch for choosing the power supply source. You can use the internal backplane supply or an external 24 VDC source rated at 195 mA maximum. That flexibility simplifies wiring in cabinets where backplane power is already near its limit.
Applications in Real Systems
The 1746-NO4I fits naturally into several industrial scenarios:
- PID control loops: Assign the analog output to represent the control output of a PID controller, driving valves, dampers, or variable frequency drives.
- Manual loading stations: Use the output to represent an operator-entered command for manual control of field devices.
- Signal retransmission: Re-transmit critical process signals to indicators, data loggers, or secondary control systems for monitoring and recording.
In each case, the module’s 0 to +20 mA range and 14-bit resolution deliver the signal fidelity your process needs.
Installation and Wiring Guidance
Install the 1746-NO4I only in a compatible 1746 chassis. The module ships with a removable terminal block, which simplifies wiring and speeds up replacement when servicing. For signal wiring, use shielded communication cable such as Belden 8761 or equivalent, and keep cable lengths as short as possible to minimize noise pickup.
Before powering up, verify your power source selection. If you choose the external supply option, confirm it provides 24 VDC ±10% at 195 mA maximum. Some applications may require 21.6 to 26.4 VDC when the SLC power supply cannot deliver enough current.
Maintenance and Reliability
The 1746-NO4I is factory-calibrated, so it does not require routine field calibration. An LED status indicator helps you confirm module operation at a glance. The module operates in ambient temperatures from 0 to 60 degrees Celsius and tolerates non-condensing relative humidity from 5 to 95%. Storage temperature ranges from -40 to 85 degrees Celsius.
For long-term reliability, inspect the terminal connections periodically and verify that cabinet cooling maintains the operating temperature within the specified range. The maximum overall accuracy drift is ±70 ppm per degree Celsius of full-scale accuracy, so stable thermal conditions support consistent performance.
Compatibility and Selection Tips
The 1746-NO4I works exclusively with the 1746 chassis and is compatible with both fixed and modular SLC 500 hardware. Before ordering, confirm your chassis type, available backplane current, and whether your application needs the external 24 VDC supply option.
When sourcing this module, work with a supplier who understands the SLC 500 platform. SpareTechPLC specializes in industrial automation parts and can help you verify compatibility and availability. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
